Data in the City

Question

How can we ask an asynchronous PowerShell job to gracefully stop on its own?

Short Answer

We can use a marker file pattern for that effect:

# this is the path to the marker file
$JobStopMarkerFile = "C:\Temp\JobStopMarker.txt";

# ensure the marker file does not exist
if (Test-Path -LiteralPath $JobStopMarkerFile)
{
    Remove-Item $JobStopMarkerFile
}

# this contains the script to run async
$JobScript = {

    param
    (
        [Parameter(Mandatory = $true)]
        $JobStopMarkerFile
    )

    # this flag will be set when the job is done
    $IsJobDone = $false

    # this condition checks whether
    # 1) the job is done
    # 2) the job has been asked to stop
    while (-not $IsJobDone)
    {
        # some recurring task would run here instead
        Start-Sleep -Seconds 5

        # uncomment and set this whenever the job finishes on its own
        # $IsJobDone = $true

        # check if the marker file exists
        if (Test-Path -LiteralPath $JobStopMarkerFile)
        {
            # signal the job as completed
            $IsJobDone = $true;

            # cleanup the file too
            Remove-Item -LiteralPath $JobStopMarkerFile
        }
    }
}

# start the job now
$Job = Start-Job -ScriptBlock $JobScript -ArgumentList $JobStopMarkerFile

# do some other stuff here
Start-Sleep 1

# ask the job to stop
# we do this by *creating* an empty marker file
# the job itself will remove this file
$null > $JobStopMarkerFile

# wait for the job to finish
Wait-Job $Job

There is quite some code here, isn’t there? So how does it work?

Long Answer

If we just want to stop a job, minus the gracefully bit, we can simply use the Stop-job Cmdlet:

Continue reading “How To Gracefully Stop An Asynchronous Job In PowerShell” →